Current tooth decay (dental caries) prevention methods include enamel hardening with fluoride and bacterial removal via mechanical and general antimicrobial approaches. These methods are based on the knowledge that oral plaque bacteria ferment dietary carbohydrates to produce pH-reducing organic acids. Initial reductions in caries incidence observed upon widespread implementation of these measures reached a plateaudecades ago. Today more that 40% of children under 10 years of age as well as more than 85% of the adult population in the United States still suffer from the disease that cause annual treatment cost of $ 80 billion. Further development of these remove and kill all approaches are not likely to significantly improve oral health. Revolutionary advancements can only be achieved by expanding our understanding of the microorganism- mediated processes leading to tooth decay. This will require a detailed picture of dental plaque organisms, their metabolic activities and interactions. The long-term objective of this application is to combine and apply (established) advanced technologies to provide a detailed understanding of the biological processes involved in cariogenesis. This will include a comprehensive analysis of the cariogenic potential of known pathogens and their influence on acid production. Furthermore, we will provide information on the metabolic activity of species whose function in acid production is currently unknown. In compliance with the mission of the NIDCR we will further develop targeted strategies against the current caries epidemic based on current knowledge and the new information developed with the advanced technologies in this project. We will combine sophisticated, species-specific in vivo labeling tools (monoclonal antibodies and fluorescent protein-expressing bacteria) with monitoring of acid production (pH-sensitive dyes, fluorescent proteins and NMR profiling), labeling of acid active species with stable isotope probing (SIP). These tools will reveal details of the processes in dental plaques regarding species, interspecies interactions and the metabolic processes contributing to cariogenic (acid-producing) or healthy (homeostatic) conditions. The second goal of this application will examine the potential of our previously developed specifically targeted antimicrobial peptides (STAMPs) against cariogenic Streptococcus mutans to shift plaque ecology towards a healthy plaque. We will further improve a current prototype antimicrobial peptide that is activated in acidic environments and develop more antimicrobial peptides against known cariogenic species as well as those identified in this project. This study will greatly expand our knowledge of the biological processes within plaques that lead to disease and provide novel therapeutic approaches that aim to achieve long-term oral health by specifically removing cariogenic species and leaving beneficial or harmless populations intact.